Three-Dimensional (3D) Bicontinuous Hierarchically Porous Mn<inf>2</inf>O<inf>3</inf> Single Crystals for High Performance Lithium-Ion Batteries

Bicontinuous hierarchically porous Mn<inf>2</inf>O<inf>3</inf> single crystals (BHP-Mn<inf>2</inf>O<inf>3</inf>-SCs) with uniform parallelepiped geometry and tunable sizes have been synthesized and used as anode materials for lithium-ion batteries (LIBs). The monodispersed BHP-Mn<inf>2</inf>O<inf>3</inf>-SCs exhibit high specific surface area and three dimensional interconnected bimodal mesoporosity throughout the entire crystal. Such hierarchical interpenetrating porous framework can not only provide a large number of active sites for Li ion insertion, but also good conductivity and short diffusion length for Li ions, leading to a high lithium storage capacity and enhanced rate capability. Furthermore, owing to their specific porosity, these BHP-Mn<inf>2</inf>O<inf>3</inf>-SCs as anode materials can accommodate the volume expansion/contraction that occurs with lithium insertion/extraction during discharge/charge processes, resulting in their good cycling performance. Our synthesized BHP-Mn<inf>2</inf>O<inf>3</inf>-SCs with a size of ~700 nm display the best electrochemical performance, with a large reversible capacity (845 mA h g^-1 at 100 mA g^-1 after 50 cycles), high coulombic efficiency (>95%), excellent cycling stability and superior rate capability (410 mA h g^-1 at 1 Ag^-1). These values are among the highest reported for Mn<inf>2</inf>O<inf>3</inf>-based bulk solids and nanostructures. Also, electrochemical impedance spectroscopy study demonstrates that the BHP-Mn<inf>2</inf>O<inf>3</inf>-SCs are suitable for charge transfer at the electrode/electrolyte interface.